Temperature responsive device



Patented Aug. 8, 1950 2.51am 'rnursaa'ruas aasrousrvs nsvloa Robert Roger Bottoms, Crestwood} Kr. assignor to National Cylinder Gas Company, Chicago, 111., a corporation of Delaware Application May 18, 1947, Serial 110,741,778

9 Claims. 1

My invention relates, generally, to temperature responsive devices, and it has particular relation to such devices for measuring small changes in ambient temperature for the determination of the constituents of gases by the thermal conductivity method although its use is not limited to this particular application.

Among the objects of my invention are: to measure slight variations in ambient temperature; to amplif the temperature changes so that the same can be measured with a high degree of accuracy; to employ resistance means subject to the temperature being measured and to change its resistance to a greater extent than the same would be changed as a result of the change in temperature alone; to employ a combination of low and high temperature coemcient v resistors subject to the temperature being measured and energized from a constant voltage source for changing the resistance of said resistance means; andto measure the resistance of said resistance means for determining the temperature.

Other objects of my invention will. in part. be obvious and in part appear hereinafter.

Accordingly. my invention is disclosed in the embodiment thereof shown in the accompanying drawing and it comprises the features of construction, combination of elements, arrangement of parts and circuit connections described hereinafter, and the scope of the application of p which will be indicated in the appended claims. For a more complete understanding of the nature and scope of my invention, reference may be had to the following detailed description taken together with the accompanying drawing, in which the single flgure illustrates, cally, a preferred embodiment of my invention.

Referring now particularly to the drawing, it will be observed that the reference character ll designates a resistor having a high temperature coeiilcient of resistance and that its terminals are indicated at H and II. The resistor it may be formed of iron, nickel, platinum or the like. so that the same will have a relatively high positive temperature coemcient of resistance with the result that, on change in the temperature to which it is subjected, there is a relatively large change in its electrical resistance.

Connected in shunt with resistor I I and subiect to the same ambient temperature is a resister I! which has a low temperature coemcient of resistance. The resistor it may have a substantially zero temperature coemcient of resistance and may be formed of any well-known material that will provide such a temperature characteristic, such as copper or copper it that has slow temperature coeiilcient oirez 'I'hereslstors lland il,asshown,areeonnectedinseriescircuitrelationwitha sistanceandmaybeformedofthesamematerlal asresistor it. has matter of fact, the "and ilmaybe'aaa with the resistor ll connected in relation with'a part thereof, such as the part it.

,Oneterminaloftheresistor ilisindicatedat II.

The resistors ll. and II may be energised from a suitable current source having a voltage. l'br example, they responding increase in the heat generated thereby.

It remains then to provide means for measuring the heat generated bythe resistor I! so that. by determining the increase in heat generated, it is powble to determine the increase in ambient temperature.

With a view to measuring the heat generated by the resistor it. a resistor I I may be employed having a high temperature coenlcient of resistance, and it may be either a positive or a negative temperature coemcient. For purposes of the present invention, the resistor Il may be formed of the same material as the resistor II and thus it may have a high positive temperature coemcient of resistance. although it will be understood that it is within the purview of my invention to employ a material having a high negative temperature vcoeilicient of resistance for the resistor ll.

Since the resistor It has a high temperature coemcient of resistance, there will be a relatively great change in its resistance on change in heat generated by the resistor l3. Thus, assuming that the resistor I8 is subjected to the same ambient temperature as the resistors l and it, there will be substantially greater change in its resistance as a result of the change in heat generated by tor it under the conditions described hereinbefore, than would be the case if the change "in its resistancewere due solely to the change ambient temperature. By measuring the change in the resistance of resistor l8, it is possible to determine the change in ambient temperature, the actual value of the resistance of resistor l8 corresponding to a particular ambient temperature.

The resistance of resistor II can be measured in various ways. As illustrated in the drawing, the resistor I! may form one leg of a Wheatstone bridge that is indicated, generally, at [9. The other legs of the bridge I! are indicated at 20, II and 22. The bridge I! can be energized from a suitable source of constant voltage, such as a battery 23. A galvanometer 24 may be employed for measuring the degree of unbalance of the bridge It. It may have a pointer 25 that swings over a scale 28 which, it will be understood, may be calibrated in terms of ambient temperature.

In the determination of the constituents of gases, such for example as the carbon dioxide content in nitrogen or air or the argon content in oxygen and like determinations, the overall change in voltage through conventional temperature responsive elements with slight temperature change is relatively low when the same are employed for this purpose. When the temperature measuring means, constructed in accordance with my invention as herein disclosed, is employed, it is possible to obtain substantially double the response for a given temperature change than is possible using the prior art apparatus. This makes it possible to obtain a higher degree of accuracy for the temperature measurements and to provide more rugged and reliable equipment than has heretofore been available.

Since certain further changes can be made in the foregoing construction and circuit connections and different embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawing and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In temperature responsive means, in combination, low temperature coefficient resistance means adapted to be energized from a constant voltage source, high temperature coefficient resistance means connected in shunt circuit relation with a part of said low temperature coefficient resistance means whereby on change in ambient temperature the voltage drop across said shunted part of said low temperature coefllcient resistance means is changed, and temperature responsive means in heat transfer relation to said shunted part of said low temperature coefilcient resistance means for measuring the change in resistanceof the first resistor.

4 heat generated thereb resulting from current flow therethrough on change in ambient temperature.-

2. The invention, as set forth in claim 1, wherein the second mentioned resistance means has a high positive temperature coefilcient of resistance.

3. In temperature responsive means, in combination, low temperature coefficient resistance means adapted to be energized from a constant voltage source. high temperature coemcient resistance means connected in shunt circuit relation with a part of said low temperature coefiicient resistance means whereby on change in ambient temperature the voltage drop across said shunted part of said low temperature coefficient resistance means is changed; high temperature coefficient resistance means disposed in heat transfer relation to said shunted part of said low temperature coeflicient resistance means, and means for measuring the resistance of the last mentioned high temperature coefilcient resistance means.

4. The invention, as set forth in claim 3, wherein the second and last mentioned resistance means each has a high positive temperature coefiicient of resistance.

5. The invention, as set forth in claim 4. wherein the resistance measuring means comprises a Wheatstone bridge circuit, and the-last mentioned resistance means is included in one leg thereof.

6. In temperature responsive means, in combination, a first resistor having a high temperature coeflicient of resistance, a second resistor having alow temperature coefilcient of resistance disposed in heat transfer relation with said first resistor, athird resistor having a high temperature coeflicient of resistance connected in parallel with said second resistor, and a fourth resistor having a low temperature coefllcient of resistance connected in series with said parallel connected second and third resistors, said resistors being subject to the same ambient temperature and said second, third and fourth resistors being arranged to beenergized from a current source whereby the resistance of said first resistor changes on variation in the ambient temperature substantially more than it changes as a result of variation in ambient temperature alone.

7. The invention. as set forth in claim 6, wherein means are provided for measuring the 8. The invention, as set forth in claim 7. wherein the first and third resistors each has a high positivetemperature coefilcient of resistance.

9. The invention, as set forth in claim 6, wherein a Wheatstone bridge circuit is provided for measuring the resistance of the first resistor and said first resistor is included in one leg of said bridge circuit.

ROBERT ROGER BOTTOMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2.163.297 Waage June 20, 1939 2,230,779 Johnson Feb. 4. 1941 

